In several applications, it is desirable to be able to select one of several optical paths for conveying a light beam. For example, in the conventional single lens reflex camera a mirror coupled to the shutter release is used selectively to direct the incoming light beam from a scene being photographed to the viewfinder or to permit the beam to strike the photographic emulsion. In the case of the SLR camera, where broad light beams are concerned, an error in positioning of the mirror or other optical switching element generally affects only the extreme edges of the beam and thus the means for mounting the mirror do not have to meet very strict criteria in this respect. In the case of a very narrow light beam, such as that which might be provided at the output of an optical fiber or which might need to be directed into an optical fiber or onto a photodetector, an error in positioning of the switching element would generally have much more serious consequences. It has hitherto been conventional to use an optical bench or other similarly massive device to ensure accurate positioning of an optical switching element used for directing a light beam selectively from a single source to one of several destinations or to select a single light beam, from several available beams, for directing towards a particular destination. However, an optical bench is inconvenient and does not lend itself well to incorporation in a portable instrument.